A mysterious ailment is causing algal blooms and killing dolphins, manatees, and pelicans along the Indian River Lagoon, one of the most valuable and diverse ecosystems in North America.

"The Indian River Lagoon on Florida's east coast has long been known as the most diverse ecosystem in North America.

Its 156 miles of water boast more than 600 species of fish and more than 300 kinds of birds.

The lagoon is not just an ecological treasure. To the towns along its edge — Titusville, Cocoa, Melbourne, Vero Beach and Stuart, among others — it accounts for hundreds of millions in revenue from angling, boating, bird-watching, tourism and other waterfront activities.

But these days the Indian River Lagoon has become known as a killing zone.

Algae blooms wiped out more than 47,000 acres of its sea grass beds, which one scientist compared to losing an entire rainforest in one fell swoop.

Then, beginning last summer, manatees began dying. As of last week, 111 manatees from Indian River Lagoon had died under mysterious circumstances. Soon pelicans and dolphins began showing up dead too — more than 300 pelicans and 46 dolphins so far.

How bad is it? In the past week, a dolphin a day has turned up dead in the lagoon, said Megan Stolen, a research scientist at Hubbs-SeaWorld Research Institute."